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85 lines
3.0 KiB
Markdown
85 lines
3.0 KiB
Markdown
# Asterinas OSTD
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> Confucious remarked,
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> "I could follow whatever my heart desired
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> without transgressing the law."
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>
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> 子曰：
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> "从心所欲，不逾矩。"
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With the Asterinas OSTD (Operating System Standard Library),
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you don't have to learn the dark art of unsafe Rust programming
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and risk shooting yourself in the foot.
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You will be doing whatever your heart desires,
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and be confident that your kernel will never crash
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or be hacked due to undefined behaviors,
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even if today marks your Day 1 as a Rust programmer.
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## APIs
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Asterinas OSTD stands
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as a powerful and solid foundation for safe kernel development,
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providing high-level safe Rust APIs that are
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1. Essential for OS development, and
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2. Dependent on the use of unsafe Rust.
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Most of these APIs fall into the following categories:
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* Memory management (e.g., allocating and accessing physical memory pages)
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* Task management (e.g., context switching between kernel tasks)
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* User space (e.g., manipulating and entering the user space)
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* Interrupt handling (e.g., registering interrupt handlers)
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* Timer management (e.g., registering timer handlers)
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* Driver support (e.g., performing DMA and MMIO)
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* Boot support (e.g., retrieving information from the bootloader)
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* Synchronization (e.g., locking and sleeping)
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To explore how these APIs come into play,
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see [the example of a 100-line kernel in safe Rust](a-100-line-kernel.md).
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The OSTD APIs have been extensively documented.
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You can access the comprehensive API documentation by visiting the [docs.rs](https://docs.rs/ostd/latest/ostd).
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## Four Requirements Satisfied
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In designing and implementing OSTD,
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we have risen to meet the challenge of
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fulfilling [the aforementioned four criteria as demanded by the framekernel architecture](../kernel/the-framekernel-architecture.md).
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Expressiveness is evident through Asterinas Kernel itself,
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where all system calls,
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file systems,
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network protocols,
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and device drivers (e.g., Virtio drivers)
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have been implemented in safe Rust
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by leveraging OSTD.
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Adopting a minimalist philosophy,
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OSTD has a small codebase.
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At its core lies the `ostd` crate,
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currently encompassing about 10K lines of code - a figure
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that is even smaller than those of many microkernels.
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As OSTD evolves,
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its codebase will expand,
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albeit at a relatively slow rate
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in comparison to the OS services layered atop it.
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The OSTD's efficiency is measurable
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through the performance metrics of its APIs
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and the system calls of Asterinas Kernel.
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No intrinsic limitations have been identified within Rust
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or the framekernel architecture
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that could hinder kernel performance.
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Soundness, unlike the other three requirements,
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is not as easily quantified or proved.
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While formal verification stands as the gold standard,
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it requires considerable resources and time
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and is not an immediate priority.
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As a more pragmatic approach,
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we will explain why the high-level design is sound
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in the soundness analysis and rely on the many
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eyes of the community to catch any potential flaws
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in the implementation.
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